Second monitor on dual-head I915 video not initialized sometimes

[Kalin Nakov]

Hello,

Our problem concerns the i810 driver.  Sometimes, once in 40-50 hard
restarts of the computer the second monitor does not start. Our system has a
dual-head I915 video embedded in the north bridge. The two independent
outputs of the video go into two monitors. The X config file is configured
with two monitors. In the rare cases when the second monitor does not start,
we have measured the output of the second video card inside the north bridge
with oscilloscope and found out that there is absolutely no signal going out
of the north bridge. I still don't know if the problem is in the hardware or
in the software, but I believe there is some code in the i810 driver that
disables or enables the video output depending on the circumstances. Maybe
because of some racing condition sometimes the second video card gets
disabled.

Here is the output of lspci -v
00:02.0 VGA compatible controller: Intel Corporation Mobile 915GM/GMS/910GML
Express Graphics Controller (rev 04) (prog-if 00 [VGA])
        Subsystem: Intel Corporation Mobile 915GM/GMS/910GML Express
Graphics Controller
        Flags: bus master, fast devsel, latency 0, IRQ 7
        Memory at fdf00000 (32-bit, non-prefetchable) [size=512K]
        I/O ports at ff00 [size=8]
        Memory at d0000000 (32-bit, prefetchable) [size=256M]
        Memory at fdf80000 (32-bit, non-prefetchable) [size=256K]
        Capabilities: [d0] Power Management version 2

00:02.1 Display controller: Intel Corporation Mobile 915GM/GMS/910GML
Express Graphics Controller (rev 04)
        Subsystem: Intel Corporation Unknown device 2592
        Flags: bus master, fast devsel, latency 0
        Memory at fde80000 (32-bit, non-prefetchable) [size=512K]
        Capabilities: [d0] Power Management version 2

If this problem could be caused by the i810 driver, where should I look in
the source to try to fix it? I am not a driver developer and certainly will
find difficulties fixing this, but anyway any help on this will be highly
appreciated.

Thank you very much in advance,
Kalin
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